A little nice puzzle

You are given 8 balls. One of the balls is heavier than the rest which are all the same weight. It is impossible to determine the heavier ball by the shape, size or lifting it up. You are given a 2-plated beam balance. Using the balance twice, how can you determine which ball is heavier.

Practice makes a man perfect.There is no substitute to hard workAll of us do not have equal talents but everybody has equal oppurtunities to build their talents.-APJ Abdul Kalam